Low-loss silicon waveguides with sidewall roughness reduction using a SiO2 hard mask and fluorine-based dry etching
01 January 2015
High optical field confinement-possible silicon waveguides is generally used in various fields. The performance of silicon waveguide depends on the sidewall roughness of silicon waveguides, which is responsible for scattering loss. The fabrication process of silicon waveguide which contains smooth sidewall for a low-loss was studied. The propagation loss of an optical silicon waveguide was reduced using a SiO2 hard mask and reactive ion etching (RIE) with fluorine gases. The sidewall angle was controlled by Si etching with a SF6 and CF4 gas mixture. The thickness of the SiO2 hard mask affects the sidewall smoothing treatment. The roughness of sidewall was reduced in the SiO2 etching process with a CF4 and O2 gas mixture as the thickness of the SiO2 hard mask was increased. The minimum propagation loss (0.89 dB/cm) of the fabricated silicon waveguide was achieved by introduced fabrication method.
